avoid_unused_constructor_parameters   
            
            Avoid defining unused parameters in constructors.
This rule is available as of Dart 2.0.0.
This rule has a quick fix available.
Details
AVOID defining unused parameters in constructors.
BAD:
class BadOne {
  BadOne(int unusedParameter, [String unusedPositional]);
}
class BadTwo {
  int c;
  BadTwo(int a, int b, int x) {
    c = a + b;
  }
}
Usage
To enable the avoid_unused_constructor_parameters rule,
add avoid_unused_constructor_parameters under linter > rules in your
analysis_options.yaml
file:
linter:
  rules:
    - avoid_unused_constructor_parameters